Thinwall guide catheter

ABSTRACT

An apparatus and method of making a thinwall guide catheter useful in delivery of therapeutic devices through a body vessel. The method comprises braiding a flat wire over the surface of a cylindrical core, placing a heat bondable polymer tube over the braid, surrounding the polymer tube with a heat shrink sleeve, heating the assembly to a temperature and for a time period sufficient to expand the core into braid interstices and bond the polymer tube to substantially only the outer surface of the braid and finally removing the heat shrink sleeve and core. The resulting guide catheter has approximately half the wall thickness of prior guide catheters and has excellent column stiffness and kink resistance.

FIELD OF THE INVENTION

This invention relates to a thinwall guide catheter for insertion intobody vessels to deliver a therapeutic device to a selected site and,more specifically, to an improved guide catheter and method of making,the guide catheter having a thinner wall and excellent stiffness, kinkresistance and torque transfer characteristics.

BACKGROUND OF THE INVENTION

Present guide catheters generally are formed as a three layer compositetube. A liner is utilized to provide a lubricious surface to aid indevice passage through the lumen of the guide. The next layer is a braidmaterial, typically a stainless steel round wire braid, which ispositioned directly over the liner. An outer jacket encapsulates thebraid and is bonded to the liner through braid interstices to create amonolithic structure from the three components. Typically a liner madein this manner is about 0.002 in. thick, the braid is 0.002 in. thick(0.004 at the crossovers) and the outer jacket thickness is dictated bythe outside diameter of the catheter. Typical overall guide catheterwall thicknesses are about 0.010 in., providing a 0.086 in. diameterlumen on an about 0.106 in. catheter. Thinner guide catheter walls aredesirable to provide maximum lumen diameter for passage of therapeuticdevices.

Guide catheters are typically used in procedures such as percutaneoustransluminal coronary angioplasty (PTCA) which are intended to reducearterial build-up of cholesterol fats or atherosclerotic plaque.Typically a guidewire is steered through the vascular system to the siteof therapy. A guiding catheter can then be advanced over the guidewireand finally a balloon catheter advanced within the guiding catheter overthe guidewire. A thin wall on the guide catheter will permit passage ofa balloon having greater diameter, as is often necessary or desirable.

A number of different catheters have been developed that use braided orcoiled reinforcing strands embedded in a plastic wall. Typical of theseare the catheter structures described by Truckai in U.S. Pat. No.5,176,660, Samson in U.S. Pat. No. 4,516,972 and Jaraczewski in U.S.Pat. No. 4,817,613. While providing acceptable torque and columnstrength, these arrangements tend to show low kink resistance and haveundesirably thick walls.

Thus, there is a continuing need for improvements in guide cathetershaving reduced wall thicknesses with resulting increased lumen diameterswhile providing improved stiffness and torque transfer characteristicsand high kink resistance.

SUMMARY OF THE INVENTION

The above noted problems are overcome by an apparatus and method ofmaking guide catheters which, comprises the steps of providing adisposable core, braiding a flat metal wire over the core, pressing aheat bondable polymer tube over the braid and heating the assembly forsufficient time to bond the tube only to the outer surface of the braid.

A guide catheter made according to the method of this invention can havea wall thickness of about 0.005 inch, approximately half of thethickness required in conventional catheters to produce comparablephysical characteristics including kink resistance and column strength.

Any suitable core material may be used. The core material should havesufficient strength to resist pressure during the heat bonding step,should not bond to the heat bonding polymer and should have low frictionwith the braid for easy removal. A solid fluorocarbon polymer ispreferred for the core. While in some cases the core can be simply slidout of the braided tube, in some cases it is preferred that ends of thecore extending beyond the braided tube be grasped and pulled apartslightly to stretch the core and reduce the cross section of the core toaid in sliding the core from the tube.

Wire may be braided in any suitable manner to form the braided tube. Thebraid is formed from a stiff flat wire, preferably a stiff metal havinga width from about 0.005 to 0.015 inch and a thickness of from about0.0007 to 0.0010 inch.

A heat shrink sleeve is used to perform the heat bonding. The heatshrink sleeve can be formed from any suitable material in a conventionalmanner. Typical heat shrink materials include fluorinatedethylene-propylene, tetrafluoroethylene and polyesters. Of these, anoptimum combination of shrink pressure and shrinking temperature isfound with fluorinated ethylene-propylene.

Preferably, a lubricant is coated onto the internal guide cathetersurface to allow a balloon catheter or other device to be inserted intothe guide catheter to be inserted and removed using less force.

It is, therefore, an object of this invention to provide an improvedthinwall guide catheter with improved physical characteristics. Anotherobject is to provide a thinwall guide catheter including a flat wirebraid wherein the braid density or "pic count" is dynamically variablein response to bending, axial, or torsional loads. Another object is tomake a thinwall guide catheter wherein the jacket is of variablethickness to permit dynamic expansion or contraction in response tobending, axial, or torsional loads. Another object is to make a thinwallguide catheter having improved kink resistance and column stiffness. Yetanother object is to produce a thinwall guide catheter capable ofbending to a smaller radius in a body lumen than conventional catheterswhile avoiding kinking.

BRIEF DESCRIPTION OF THE DRAWINGS

Details of the invention, and of preferred embodiments thereof, will befurther understood upon reference to the drawing, wherein:

FIG. 1 is an axial section view through a thinwall guide catheter ofthis invention;

FIG. 2 is a transverse section view, taken on line 2--2 in FIG. 1;

FIG. 3 is a flow chart illustrating the steps in the guide cathetermanufacturing method of this invention;

FIG. 4 is a perspective view of a newly completed thinwall guidecatheter upon completion of manufacture and prior to removal of shapingcomponents, with portions cut away;

FIG. 5 is a section view taken on line 5--5 in FIG. 4 with the core inan expanded state;

FIG. 6, is a portion of FIG. 4 with the core removed from the catheter;and

FIG. 7 is a view of FIG. 2 in a bent configuration such that the piccount is greater on the inside of the bending radius than on the outsideof the bending radius.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, there is seen axial and transverse sectionviews, respectively, through a thinwall guide catheter 10 made inaccordance with this invention. A braided tube 12 of wires 14 is bondedwithin a polymer tube jacket 16. While a fairly loose braid density isshown for clarity, a tight braid density is often preferred. Jacket 16is bonded to the outer surfaces of braided tube 12, with little materialin the interstices 48 between adjacent wires 14 and essentially nopolymer overlapping the inside surface of the braided tube 12.

The cross section of wires 14 may be generally rectangular, preferablywith rounded edges. Alternatively, the cross section may be generallyoval or elliptical, if desired. An optimum flat wire material is fullytempered 304 stainless steel. The selected wire is braided in aconventional manner over the core. Any suitable braid configuration, inparticular any suitable pic count may be used. A braided tube 12 withfrom about 45 to about 55 cross-overs per inch is preferred. About 50cross-overs per inch being the most optimum. Wires 14 define a "one(wire) under-one (wire) over" braiding pattern so that the wires 14 forman interlocking mesh with each other. For best results, the wires 14have thicknesses of from about 0.0007 to 0.0010 inch and widths of fromabout 0.010 to 0.015 inch. Optimum results are achieved with a 0.0007in. thick braid producing a 0.0014 in. thickness at the crossovers.

Any suitable polymer that will bond to wires 14 when heated to asuitable temperature may be used for the jacket 16. Typical suchpolymers include polyether block amides, polyurethanes, polyethylene,Polyamides and mixtures thereof. Of these, optimum results are obtainedwith the PEBAX® brand polyether block amide available from the ElfAtochem Corporation, Philadelphia, Pa. Using a jacket 16 having anaverage thickness of about 0.0036 inch, overall wall thicknesses ofabout 0.005 inch are achieved. A reduction of wall thickness fromprevious catheters is thus about 50%. This provides an 0.084 inch lumenin a 7 French (0.094 inch) catheter.

FIG. 3 is a flow diagram illustrating the steps in the manufacture ofthe improved thinwall guide catheter of this invention. FIG. 4 shows aperspective view, partly cut away, of the assembly for manufacturing theimproved catheter.

A core 18 is provided, as indicated in step 20, around which the flatwire 14 can be braided as indicated in step 22. Any suitable corematerial that will withstand the processing conditions and can be easilyremoved from the product tube may be used. The material of core 18,however, should be softer than that of the jacket 16 so that the corematerial will expand into the interstices 48 of the braided tube 12under the temperatures and pressures of the heat bonding process toessentially the outer surface of the braided tube 12. Typical corematerials include fluorocarbon resins, such as tetrafluoroethylene andfluorinated ethylene-propylene resins. Of these, best results areobtained with tetrafluoroethylene, available under the Teflon® trademarkfrom the E.I. duPont de Nemours & Co.

The jacket 16, in the form of a tube, is then placed over braided tube12 on core 18, as indicated in step 24. A length of heat shrink sleeve26, in the form of a tube, is then placed over the jacket 16, asindicated in step 28. Heat shrink sleeve 26 should be selected inmaterial and thickness to provide the optimum pressure at an optimumtemperature. Best results are obtained with fluorinatedethylene-propylene resins of the sort available from the E.I. duPont deNemours & Co.

The resulting assembly is heated to shrink the heat shrink sleeve 26 andbond the jacket 16 to the braided tube 12, as indicated in step 30. Anysuitable time, temperature and heating method may be used. Insufficienttime and/or a lower than necessary temperature will result in a poorbond between jacket 16 and braided tube 12 and undesirably low stiffnessvalues. Excessive time and/or excessively high temperatures will resultin substantial encapsulation of the braided tube 12 by the jacket 16.This produces a great reduction in angular deflection to kink.

Through the proper selection of core material and processing conditions,the jacket 16 will be bonded only to the outer surface of the braidedtube 12. Optimum processing conditions for a particular material for thejacket 16 can be easily obtained by making a series of catheters usingdifferent combinations of heating time and temperature. The catheterscan be examined to determine the combination of time and temperaturethat produces catheters having the desired bonding to only the outersurface of the braided tube 12, which results in an optimum combinationof column strength and kink resistance for an intended catheter end use.

Upon completion of the heating step, generally with cooling to roomtemperature, heat shrink sleeve 26 is stripped away as indicated by step32 and core 18 is withdrawn as shown in step 34. Preferably, core 18 isslightly stretched to slightly reduce core cross section and easeremoval. Preferably, after the core 18 is removed, a lubricant such as asilicone lubricant, is coated over the inside surface of braided tube 12to facilitate device movement within the catheter 10.

FIG. 5 is a section through the assembly of FIG. 4, taken on line 5--5during the heating step. This section passes through the cross-overpoints of the individual wires 14 of the braided tube 12. As seen, core18 has expanded into the interstices 48 of the braided tube 12 so thatthe material of jacket 16 cannot penetrate into them. The "bulges" 17 inthe core 18 at the interstices 48 of the braided tube 12 will retractwhen core 18 is cooled and can be further loosened when the ends of thecore 18 are moved apart to stretch and reduce the cross-section of thecore 18. Preferably, the ends of the core 18 are pulled away from eachother to stretch the core 18 and reduce core diameter to allow easywithdrawal of the core 18 from the completed catheter 10.

Referring to FIG. 6, which is a section through the assembly of FIG. 4with the core 18 of FIG. 5 removed from the catheter 10. The bulges 17in the core 18 of FIG. 5 produce voids 19 in the jacket 16 at eachinterstitial location 48 between preferably four (4) adjacent cross-overpoints 44 of braided tube 12. The cross-over points, 44, define an outersurface 45, an inner surface 46, and an intermediate surface 47. Thevoids 19 in the jacket 16 are generally hemispherical in shape,producing corresponding variable thicknesses of the jacket 16 betweenthe cross-over points 44 of the braided tube 12. The jacket 16 varies inthickness from a minimum in the center of the four respective cross-overpoints 44 of the braided tube 12 to a maximum at the junctions of thejacket 16 with the outer surface 45 of the respective cross-over points44 of the braided tube 12. The effect of the voids 19 in the jacket 16is that when the catheter 10 is subjected to bending, axial, ortorsional loading, the jacket 16 is permitted to dynamically expand andcontract within the interstices 48 of the braided tube 12 in response tothe loads and thus resist a buckling failure.

With jacket 16 bonded only to the outer surface of braided tube 12, andthe wires 14 forming a "one under-one over" braiding pattern asdescribed above, the wires 14 are preferably bonded to the jacket 16 atevery other cross-over point 44, with the cross-over points 44therebetween being free from a bond with jacket 16. As a result of thispreferred bonding geometry, when a region along the catheter is bent,the segments of individual wires 14 which are between adjacent points ofbonding with the jacket 16 can move in response bending, axial, ortorsional loading. For example, as seen in FIG. 7 segments of wire 14are permitted to move toward each other on the inside of a bendingradius and move apart at the outside of the bending radius, providing aresistance to kinking of the catheter 10. The effect of the wires 14moving relative to each other in response to bending or torsion of thecatheter results in a dynamically variable pic count in the catheter.This ability to vary the pic count at bends is of great importance inavoiding catheter kinking in use. Thus, the two-fold effect of a jacket16 which is permitted to dynamically expand and contract within theinterstices 48 of the braided tube with a dynamically variable pic countresults in superior performance in the thinwall guide catheter.

With jacket 16 bonded only to the outer surface 45 of the cross-overpoints 44 of the braided tube 12, and the wires 14 forming a "oneunder-one over" braiding pattern as described above, the individualwires 14 are preferably bonded to the jacket 16 at every othercross-over point at the outer surfaces 45. The jacket 16, however, isneither bonded to the inner surface 46, nor bonded to the intermediatesurface 47 of the cross-over points 44 at the outer surface, with thecross-over points therebetween being free from a bond with jacket 16. Asa result of this preferred bonding geometry, when a region along thecatheter is bent, the segments of individual wires 14 which are betweenadjacent points of bonding with the jacket 16 can move in responsebending, axial, or torsional loading. For example, segments of wire 14are permitted to move toward each other on the inside of a bendingradius and move apart at the outside of the bending radius, providing aresistance to kinking of the catheter 10. The effect of the wires 14moving relative to each other in response to bending or torsion of thecatheter results in a dynamically variable pic count in the catheter.This ability to vary the pic count at bends is of great importance inavoiding catheter kinking in use.

The following examples provide further preferred embodiments of thecatheter manufacturing method of this invention. Parts and percentagesare by weight unless otherwise indicated.

EXAMPLE I

A catheter was prepared as follows. A core of tetrafluoroethylene fromthe duPont company, having a circular cross section and a diameter ofabout 0.084 inch, was provided. The core was braided in a ModelK80/16-1K -72 braiding machine from the Steeger company with No. 304flat stainless steel wire having a width of about 0.010 inch andthickness of about 0.0007 inch in a pattern producing a pic count ofabout 50 cross-overs per inch. A tube of polyethylene block amidepolymer, available from Atochem, Inc. under the PEBAX® 7033(70D)designation was placed over the braided core. The tube has an insidediameter of about 0.087 inch and a wall thickness of about 0.004 inch. Afluorinated ethylene-propylene sleeve, available from Zeus, Inc. underthe FEP heat shrink tubing designation and having an inside diameter ofabout 0.117 inch was slipped over the PEBAX® tube. The resultingassembly was placed in a 250° C. oven for about 5 minutes, then removedand allowed to cool to room temperature. The shrink tube was removed andthe core withdrawn. The resulting tube has the outer jacket bonded toonly the outside surface of the braid. The resulting catheter hasapproximately a 40 degree improvement in angular deflection to kink whencompared to similar catheters having the braid encapsulated in thepolymer and has excellent column strength. Repeated bending of the tubedoes not significantly lower the stiffness values.

EXAMPLES II-V

The manufacturing process of Example I is repeated four times, with thefollowing differences:

Example II: Oven temperature 180° C., heating time 5 minutes,

Example III: Oven temperature 180° C., heating time 10 minutes,

Example IV: Oven temperature 250° C., heating time 7 minutes, and

Example V: Oven temperature 300° C., heating time 5 minutes.

The catheter produced in Example II has good kink resistance but lowcolumn strength. That made in Examples II and III have good kinkresistance. In Examples IV and V, the polymer tube material penetratesinto the interstices 48 of the braided tube and at least partiallyencapsulates the braid. Kink resistance is much lower than in Example I,although column strength is good.

EXAMPLE VII

An animal study was conducted, with a 35 kilogram canine with femoralcut down and using a 9F percutaneous sheath. Attempts to emplace astandard Sherpa® guide catheter was unsuccessful due to the relativelysmall canine anatomy. A guide catheter as described in Example I wassuccessfully intubated into the left coronary artery. This guidecatheter was found to be easier to turn and more responsive to movement.

While certain specific relationships, materials and other parametershave been detailed in the above description of preferred embodiments,those can be varied, where suitable, with similar results. Otherapplications, variations and ramifications of the present invention willoccur to those skilled in the art upon reading the present disclosure.Those are intended to be included within the scope of this invention asdefined in the appended claims.

What is claimed is:
 1. A thinwall guide catheter, comprising:anelongated braided tube, the braided tube having an outer diameter and aninner diameter, the braided tube having a plurality of elongated wires,one of each of the elongated wires being meshed with an other of each ofthe elongated wires, one of each of the elongated wires defining withthe other of each of the elongated wires a plurality of cross-overpoints, one of each of the cross-over points having an outer surface, aninner surface, and an intermediate surface, one of each of thecross-over points defining a plurality of interstices, one of each offour adjacent cross-over points defining one of each of the intersticestherebetween; an elongated jacket, the elongated jacket having an innerdiameter and an outer diameter, the inner diameter of the elongatedjacket being disposed over the outer diameter of the braided tube, theelongated jacket being bonded to one of each of the outer surface of thecross-over points, the elongated jacket being unbonded to one of each ofthe intermediate surface of the cross-over points, the elongated jacketbeing unbonded to one of each of the inner surface of the cross-overpoints; so that, in response to bending, axial, or torsional loadsimpressed on the catheter, one of each of the inner and intermediatesurfaces of the cross-over points permit one of each of the elongatedwires to expand and contract relative to another of each of theelongated wires.
 2. The thinwall guide catheter according to claim 1wherein the braided tube and the elongated jacket have a combinedthickness of from about 0.004 to 0.005 inch.
 3. The thinwall guidecatheter according to claim 1 wherein the elongated wires have a widthof from about 0.005 to 0.015 inch and a thickness of from about 0.0007to 0.0010 inch and the width lies generally parallel to the outerdiameter of the braided tube.
 4. The thinwall guide catheter accordingto claim 1 wherein the elongated jacket is formed from a polymerselected from the group consisting of polyether block amides,polyurethanes, polyethylene, polyamides and mixtures thereof.
 5. Thethinwall guide catheter according to claim 1 wherein the elongated wiresare formed from 304 fully tempered stainless steel.
 6. The thinwallguide catheter according to claim 1 wherein the braided tube has apredetermined pic count along regions of the catheter when straight, ahigher pic count along the inside of regions when bent and a lower piccount along the outside surface of regions when bent.
 7. A thinwallguide catheter, comprising:an elongated braided tube, the braided tubehaving an outer diameter and an inner diameter, the braided tube havinga plurality of elongated wires, one of each of the elongated wires beingmeshed with an other of each of the elongated wires, one of each of theelongated wires defining with the other of each of the elongated wires aplurality of cross-over points, one of each of the cross-over pointshaving an outer surface, an inner surface, and an intermediate surface,one of each of the cross-over points defining a plurality ofinterstices, one of each of four adjacent cross-over points defining oneof each of the interstices therebetween; an elongated jacket, theelongated jacket having an inner diameter and an outer diameter, theinner diameter of the elongated jacket being disposed over the outerdiameter of the braided tube, the elongated jacket being bonded to oneof each of the outer surface of the cross-over points, the elongatedjacket being unbonded to one of each of the intermediate surface of thecross-over points, the elongated jacket being unbonded to one of each ofthe inner surface of the cross-over points, the elongated jacket havinga first thickness where the elongated jacket is bonded to one of each ofthe outer surface of the cross-over points, the elongated jacket havinga varying thickness over one of each of the interstices, the elongatedjacket having a minimum thickness over the center of one of each of theinterstices; so that, in response to bending, axial, or torsional loadsimpressed on the catheter, one of each of the inner and intermediatesurfaces of the cross-over points permit one of each of the elongatedwires to expand and contract relative to another of each of theelongated wires and the elongated jacket is permitted to expand andcontract over the interstices.
 8. The thinwall guide catheter accordingto claim 7 wherein the braided tube and the elongated jacket have acombined thickness of from about 0.004 to 0.005 inch.
 9. The thinwallguide catheter according to claim 7 wherein the elongated wires have awidth of from about 0.005 to 0.015 inch and a thickness of from about0.0007 to 0.0010 inch and the width lies generally parallel to the outerdiameter of the braided tube.
 10. The thinwall guide catheter accordingto claim 7 wherein the elongated jacket is formed from a polymerselected from the group consisting of polyether block amides,polyurethanes, polyethylene, polyamides and mixtures thereof.
 11. Thethinwall guide catheter according to claim 7 wherein the elongated wiresare formed from 304 fully tempered stainless steel.
 12. The thinwallguide catheter according to claim 7 wherein the braided tube has apredetermined pic count along regions of the catheter when straight, ahigher pic count along the inside of regions when bent and a lower piccount along the outside surface of regions when bent.
 13. The thinwallguide catheter according to claim 7 wherein the elongated jacket definesa generally hemispherical shape over one of each of the interstices. 14.A thinwall guide catheter, comprising:an elongated braided tube, thebraided tube having an outer diameter and an inner diameter, the braidedtube having a plurality of elongated wires, the braided tube having apredetermined pic count along regions of the catheter when straight, oneof each of the elongated wires having a width of from about 0.005 to0.015 inch and a thickness of from about 0.0007 to 0.0010 inch and thewidth lies generally parallel to the outer diameter of the braided tube,one of each of the elongated wires being formed from 304 fully temperedstainless steel, one of each of the elongated wires being meshed with another of each of the elongated wires, one of each of the elongated wiresdefining with the other of each of the elongated wires a plurality ofcross-over points, one of each of the cross-over points having an outersurface, an inner surface, and an intermediate surface, one of each ofthe cross-over points defining a plurality of interstices, one of eachof four adjacent cross-over points defining one of each of theinterstices therebetween; an elongated jacket, the elongated jackethaving an inner diameter and an outer diameter, the elongated jacket isformed from a polymer selected from the group consisting of polyetherblock amides, polyurethanes, polyethylene, polyamides and mixturesthereof, the inner diameter of the elongated jacket being disposed overthe outer diameter of the braided tube, the elongated jacket beingbonded to one of each of the outer surface of the cross-over points, theelongated jacket being unbonded to one of each of the intermediatesurface of the cross-over points, the elongated jacket being unbonded toone of each of the inner surface of the cross-over points, the elongatedjacket having a first thickness where the elongated jacket is bonded toone of each of the outer surface of the cross-over points, the elongatedjacket having a varying thickness over one of each of the interstices,the elongated jacket having a minimum thickness over the center of oneof each of the interstices, the elongated jacket defining a generallyhemispherical shape over one of each of the interstices; so that, thebraided tube and the elongated jacket have a combined thickness of fromabout 0.004 to 0.005 inch, and that, in response to bending, axial, ortorsional loads impressed on the catheter, one of each of the inner andintermediate surfaces of the cross-over points permit one of each of theelongated wires to expand and contract relative to another of each ofthe elongated wires resulting in a higher pic count along the inside ofregions when bent and a lower pic count along the outside surface ofregions when bent and the elongated jacket is permitted to expand andcontract over the interstices.